Temperature sensitive location error compensation

ABSTRACT

A system that may include a movable support module for supporting an object and a controller, wherein the controller is configured to: receive an estimated location of a movable support module that supports an object and temperature information about an actual or estimated temperature of at least a portion of the object support module; and calculate movable support module location information, in response to (a) the estimated location of the movable support module, (b) the temperature information, and (c) a mapping between (i) values of the temperature information, (ii) estimated locations of the movable support module, and (iii) location errors of the movable support module

BACKGROUND OF THE INVENTION

Objects such as wafers are manufactured by highly complicatedmanufacturing processes. These manufacturing processes should bemonitored in order to ensure the quality of the wafers.

Monitoring process may include (a) using an inspection tool forperforming an inspection process to detect potential defects, and (b)using a review tool for performing a review of the potential defects.

The inspection tool may illuminate the object by one or more beams ofelectrons, ions or by one or more beams of optical, ultraviolet, deepultraviolet or extreme ultraviolet radiation. The review tool usuallyilluminates the objects using one or more electron beams or one or morean ion beams.

Each tool of the inspection tool and the review tool may scan the object(or only parts of the object) by introducing a mechanical movementbetween the object and either the optical or electron optics.

The mechanical movement is usually introduced by a movable supportmodule that may be a mechanical stage. The mechanical stage may be anXYZ stage that is configured to support the object and to move theobject along imaginary X axis, Y axis and Z axis.

The mechanical stage location is monitored by X axis and Y axis laserinterferometers.

It has been found that laser interferometer based monitoring does notprovide adequate compensation for mechanical stage movementinaccuracies.

There is a growing need to provide a method for reducing the locationerrors in an inspection or review tool.

BRIEF SUMMARY OF THE INVENTION

According to an embodiment of the invention there may be provided asystem that may include a movable support module for supporting anobject and a controller, wherein the controller may be configured to:receive (a) an estimated location of a movable support module thatsupports an object, (b) temperature information about an actual orestimated temperature of at least a portion of the object supportmodule; and calculate movable support module location information, inresponse to (a) the estimated location of the movable support module,(b) the temperature information and, (c) a mapping between (i) values ofthe temperature information, (ii) estimated locations of the movablesupport module, and (iii) location errors of the movable support module.

The controller may be configured to calculate the mapping.

According to an embodiment of the invention there may be provided amethod for temperature sensitive location error compensation, the methodmay include: receiving, by a controller, (a) an estimated location of amovable support module that supports an object, (b) temperatureinformation about an actual or estimated temperature of at least aportion of the object support module; and calculating, by thecontroller, movable support module location information, in response to(a) the estimated location of the movable support module, (b) thetemperature information and, (c) a mapping between (i) values of thetemperature information, (ii) locations of the movable support module,and (iii) location errors of the movable support module.

The method may include calculating a location of an optical axis of aninspection or review tool in response to the movable support modulelocation information.

The method may include generating the mapping by measuring the locationerrors of the movable support module at different actual or estimatedtemperatures of the movable support module.

The method may include heating the movable support module by a heatingelement to obtain at least some of the different actual or estimatedtemperatures of the movable support module.

The method may include heating the movable support module by moving themovable support module during a period of time that exceeds apredetermined threshold to obtain at least some of the different actualor estimated temperatures of the movable support module.

The method may include cooling the movable support module by a coolingelement to obtain at least some of the different actual or estimatedtemperatures of the movable support module.

The estimated location of the movable support module may be provided bya location monitor; wherein the temperature information may be providedby a temperature sensor that may be located at a certain position;wherein the generating of the mapping may include estimating arelationship between a temperature sensed by the temperature sensor anda temperature of a part of the location monitor.

The method may include receiving the temperature information from atemperature sensor that senses a temperature of a certain portion of theobject support module.

The method may include receiving the temperature information frommultiple temperature sensors that sense temperatures of certain portionsof the object support module.

The method may include receiving temperature timing information about atiming of acquisition of the temperature information; and wherein thecalculating of the movable support module location information may bealso responsive to the temperature timing information.

The method may include calculating a change of the temperatureinformation over time; and wherein the calculating of the movablesupport module location information may be also responsive to the changeof the temperature timing information over time.

The method may include: receiving or calculating a relationship betweena scan pattern that may be followed by the movable support module andbetween temperatures obtained during the scan pattern; detecting thatthe movable support module started to follow the scan pattern; andcalculating the movable support module location information in responseto the relationship.

The movable support module may include an X-Y axis stage and a Z axisstage; wherein the movable support module location information may beindicative of a location of the movable support module within an X-Yplane; and wherein the temperature information may be provided bytemperature sensors embedded in the Z axis stage.

According to an embodiment of the invention there may be provided anon-transitory computer readable medium that may store instructions thatonce executed by a computer cause the computer to receive (a) anestimated location of a movable support module that supports an object,(b) temperature information about an actual or estimated temperature ofat least a portion of the object support module; and calculate movablesupport module location information, in response to (a) the estimatelocation of the movable support module, (b) the temperature informationand, (c) a mapping between (i) values of the temperature information,(ii) estimate locations of the movable support module, and (iii)location errors of the movable support module.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter regarded as the invention is particularly pointed outand distinctly claimed in the concluding portion of the specification.The invention, however, both as to organization and method of operation,together with objects, features, and advantages thereof, may best beunderstood by reference to the following detailed description when readwith the accompanying drawings in which:

FIG. 1 is a side view of a system according to an embodiment of theinvention;

FIG. 2 is a top view of a system according to an embodiment of theinvention;

FIG. 3 is a side view of a system according to an embodiment of theinvention;

FIG. 4 is a side view of a system according to an embodiment of theinvention;

FIG. 5 is a top view of a system according to an embodiment of theinvention;

FIG. 6 is a side view of a system according to an embodiment of theinvention;

FIG. 7 is a side view of a system according to an embodiment of theinvention;

FIG. 8 illustrates a method according to an embodiment of the invention;

FIG. 9 illustrates location errors before applying a temperaturesensitive location error correction; and

FIG. 10 illustrates location errors before applying a temperaturesensitive location error correction according to an embodiment of theinvention.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the figures have not necessarily been drawn to scale.For example, the dimensions of some of the elements may be exaggeratedrelative to other elements for clarity. Further, where consideredappropriate, reference numerals may be repeated among the figures toindicate corresponding or analogous elements.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the invention.However, it will be understood by those skilled in the art that thepresent invention may be practiced without these specific details. Inother instances, well-known methods, procedures, and components have notbeen described in detail so as not to obscure the present invention.

The subject matter regarded as the invention is particularly pointed outand distinctly claimed in the concluding portion of the specification.The invention, however, both as to organization and method of operation,together with objects, features, and advantages thereof, may best beunderstood by reference to the following detailed description when readwith the accompanying drawings.

Because the illustrated embodiments of the present invention may for themost part, be implemented using electronic components and circuits knownto those skilled in the art, details will not be explained in anygreater extent than that considered necessary as illustrated above, forthe understanding and appreciation of the underlying concepts of thepresent invention and in order not to obfuscate or distract from theteachings of the present invention.

Any reference in the specification to a method should be applied mutatismutandis to a system capable of executing the method and should beapplied mutatis mutandis to a non-transitory computer readable mediumthat stores instructions that once executed by a computer result in theexecution of the method.

Any reference in the specification to a system should be applied mutatismutandis to a method that may be executed by the system and should beapplied mutatis mutandis to a non-transitory computer readable mediumthat stores instructions that may be executed by the system.

Any reference in the specification to a non-transitory computer readablemedium should be applied mutatis mutandis to a system capable ofexecuting the instructions stored in the non-transitory computerreadable medium and should be applied mutatis mutandis to method thatmay be executed by a computer that reads the instructions stored in thenon-transitory computer readable medium.

FIG. 1 is a side view of system 11 that supports an object 90 accordingto an embodiment of the invention. System 11 may be an inspection tool(optical inspection tool or charged particle beam inspection tool), areview tool (such as but not limited to a scanning electron microscope,a transmissive electron microscope), an aerial inspection tool, astepper, a lithography tool, an atomic force microscope (AFM), and thelike.

System 11 includes an image obtaining module 20, a processor 30, amechanical stage 40 for supporting and moving an object 90, and alocation monitor 50 for monitoring the location of the mechanical stage40. The object may 90 be a wafer, a die, a flat panel display, aphotolithographic mask, a solar panel, amicro-electro-mechanical-system, a nano-electro-mechanical-system, asubstrate or any other object.

Image obtaining module 20 may include a controller 22 and optics 21. Theoptics 21 are arranged to illuminate the entire object or only parts ofthe object 90 with one or more beams. For simplicity of explanation itis assumed that the optics 21 is charged particles optics and that theyilluminate the object with a single electron beam. The optics 21 has anoptical axis 23. The electron beam may propagate along the optical axis23 or may be deflected to deviate from the optical axis 23.

The location monitor 50 of FIG. 1 is a laser interferometer thatincludes laser optics 51, first mirror 52 and second mirror 53. Thefirst mirror 52 is attached to the optics 21 while the second mirror 53is attached to an upper part of mechanical stage 40. The laser optics 51are arranged to direct a first light beam towards the first mirror 52and to direct a second light beam towards the second mirror 53. Thefirst mirror 52 and the second mirror 53 reflect the first and secondlight beams towards the laser optics 51. The reflected beams from thefirst and second mirror interfere and form an interference pattern thatis detected by the laser optics 51. It is noted that any other type oflocation monitor may be used and the laser interferometer is only onenon-limiting example of a location monitor.

The optic 21 may be static and the mechanical stage 40 may move inrelation to the optics 21.

The laser optics 51 may process the interference pattern to providedistance between the first mirror 52 and second mirror 53. This distancereflects an estimated distance between optics 21 and the mechanicalstage 40.

The distance also reflects the estimated location of the mechanicalstage 40 and/or the estimated location of the optical axis 23 of optic21. The controller 22 is fed with a relationship between the point ofincidence of the electron beam on the object and the optical axis 23(whether optics 21 deflected the beam of electrons and if so—the extentof deflection) and may estimate the location of the point of incidenceof the electron beam on the object.

The mechanical stage 40 may include a temperature sensor 45 thatmeasures a temperature of at least one point of the mechanical stage 40.The temperature sensor 45 may be integrated with the mechanical stage40, may be connected to the mechanical stage or may be thermally coupledto the mechanical stage 40.

It is noted that the temperature sensor 45 may not be included withinthe mechanical stage 40 and may measure the temperature of at least onepoint of the mechanical stage 40 even without contacting the mechanicalstage 40.

It has been found that the estimated location of the mechanical stage 40is dependent upon the temperature of various parts of the system—such asthe temperatures of different points of the mechanical stage 40 and thetemperatures of different points of the location monitor 50.

Especially—at higher temperatures the mechanical stage 40, the object 90and the location monitor 50 (especially first mirror 52 and/or secondmirror 53) tend to undergo a non- homogenous and non-linear deformationthat results in location errors. The deformation may change from onetemperature to another and from one review tool to another.

The deformation is termed non-homogenous as different parts of theobject 90, of the mechanical stage 40 and/or the location monitor 50 aredeformed at different manners. For example—FIG. 9 illustrates a map 200that includes arrows that are indicative of the location errors atdifferent points of the mechanical stage 40. The locations errors differfrom one point to another.

It should be noted that the deformation of the mechanical stage 40 maydiffer from the deformation of the first and second mirrors—due to thedifferent materials and/or different structure of the mechanical stage40 and the first and second mirrors.

According to an embodiment of the invention the controller 22 receivesfrom the laser optic 51 an estimated location of the mechanical stage40. The controller 22 may also receive temperature information about anactual temperature of at least one point of the mechanical stage 40 fromthe temperature sensor 45.

In order to determine the exact location of the mechanical stage 40—andthe exact location of the optical axis 23 of the optics 21—thecontroller 22 may use a mapping between (i) values of the temperatureinformation, (ii) estimated locations of the movable support module, and(iii) location errors of the movable support module.

The controller 22 may generate movable support module locationinformation that reflects the exact location of the movable supportmodule and may use the movable support module location information forcontrolling an image acquisition process applied by optics 21.

The mapping may be a function, may be a group of functions, may be alook up table or may be arranged in any manner. For example, thefunction may take the following format:

Correct(X,Y)=MAP {Estimated (X,Y), Temperature}.

Wherein the exact XY coordinates are denoted Correct(X,Y), MAP is amapping function, Estimated(X,Y) are estimated XY coordinates providedby laser optics 51, and Temperature represents the temperatureinformation.

According to an embodiment of the invention the mapping function mayalso be responsive to the change of temperature over time and/or totiming information (such as timestamps) indicative of a time ofacquisition of the temperature reading. In this case the mapping maytake one of the following formats:

Correct(X,Y)=MAP {Estimated (X,Y), Temperature, Timestamps}.

Correct(X,Y)=MAP {Estimated (X,Y), Temperature, Delta-Temperature}.

Wherein timing information is denoted Timestamps and changes oftemperatures over time is denoted Delta-Temperature.

A temperature sensor may sense the actual temperature of a certain pointof the system 11. The actual temperature may affect the temperature ofother points of the system 11—after a certain period of time. Thisperiod of time may be taken into account when processing the timestamps.For example—the temperature sensor 45 may sense an actual temperature ofa certain point of the mechanical stage 40. This actual temperature mayaffect the temperature of the second mirror 53 after a certain delay andthis delay will be taken into account. The temperature of the secondmirror 53 is not measured and therefore is an estimated temperature.

The mapping may be calculated by processor 30 or received by processor30. Additionally or alternatively, the mapping may be calculated orreceived by the controller 22.

FIG. 2 is a top view of system 11 that supports an object 90 accordingto an embodiment of the invention. FIG. 2 illustrates that a locationmonitor 50 that includes an X-axis interferometer (including laseroptics 51 as well as a first mirror 52 and a second mirror 53) and aY-axis interferometer that includes second laser optics 54 as well as athird mirror 55 and a fourth mirror 56. The third mirror 55 is attachedto optics 21 while the fourth mirror 56 is attached to the mechanicalstage 40.

The X-axis interferometer and the Y-axis interferometer operate at thesame manner. The X-axis interferometer provides an estimated distance(along the X-axis) between the third mirror 55 and fourth mirror56—which reflects an estimated distance (along the X-axis) betweenoptics 21 and the mechanical stage 40. The Y-axis interferometerprovides an estimated distance (along the Y-axis) between the firstmirror 52 and a second mirror 53—which reflects an estimated distance(along the Y-axis) between optics 21 and the mechanical stage 40.

The controller 22, when calculating the movable support module locationinformation may take into account the distances provided by X axis and Yaxis interferometers.

FIG. 3 is a side view of system 13 that supports an object 90 accordingto an embodiment of the invention. System 13 differs from system 11 byhaving a temperature sensor 45 that is a contactless temperature sensorand measures an actual temperature of one or more points of themechanical stage without contacting the mechanical stage—instead ofhaving a temperature sensor 45 that is included in the mechanical stage40.

FIG. 4 is a side view of system 14 that supports an object 90 accordingto an embodiment of the invention. System 14 illustrates the mechanicalstage 40 as including a Z-axis stage 41, a Y-axis stage 42 and an X-axisstage 43. The Z-axis stage 41 is located above the Y-axis stage 42 andthe X-axis stage 43. The temperature sensor 45 is included in (orconnected to) the Z-axis stage 41.

FIG. 5 is a top view of system 15 that supports an object 90 accordingto an embodiment of the invention. System 15 differs from system 11 byhaving an optical microscope 29 in addition to optics 21. The opticalmicroscope may be used for various purposes such as object alignment,coarse navigation, defect inspection and the like. In FIG. 5 thetemperature sensor 45 is located below object 90.

FIG. 6 is a side view of system 16 that supports an object 90 accordingto an embodiment of the invention. System 16 differs from system 11 byhaving a cooling element 46 for cooling the mechanical stage 40.

FIG. 7 is a side view of system 17 that supports an object 90 accordingto an embodiment of the invention. System 17 differs from system 11 byhaving a heating element 47 for heating the mechanical stage 40.

At least one of the heating element 47 of system 17 and the coolingelement of system 16 may be used to control the temperature of themechanical stage 40 and especially to reduce changes in the temperatureof the mechanical stage 40. This reduction may reduce the fluctuationsin location errors.

FIG. 8 illustrates method 100 according to an embodiment of theinvention. Method 100 may start by steps 110 or 120. Step 110 mayinclude calculating a mapping between (i) values of temperatureinformation, (ii) estimated locations of a movable support module, and(iii) location errors of the movable support module.

The temperature information is about an actual or estimated temperatureof at least a portion of the object support module.

The locations errors of the movable support module represent differencesbetween the estimated locations of the movable support module and theactual locations of the movable support module. The locations errors maybe calculated by comparing the estimated locations of the movablesupport module that are provided by a location monitor and betweenactual locations of structural elements of interest of an object that issupported by the movable support module. The actual locations of thestructural elements may be determined by an inspection or review toolthat images the object while the object is supported by the movablesupport module.

Step 110 may include measuring the location errors of the movablesupport module at different actual or estimated temperatures of themovable support module. This may include scanning the entire object byan inspection or review tool.

Step 110 may include heating the movable support module by a heatingelement to obtain at least some of the different actual or estimatedtemperatures of the movable support module.

Step 110 may include heating the movable support module by moving themovable support module during a period of time that exceeds apredetermined threshold (for example—half an hour) to obtain at leastsome of the different actual or estimated temperatures of the movablesupport module:

Step 110 may include cooling the movable support module by a coolingelement to obtain at least some of the different actual or estimatedtemperatures of the movable support module.

Step 110 may include estimating a relationship between an actualtemperature sensed by a temperature sensor and an estimated temperatureof a part of the location monitor. The location monitor provides theactual location of the movable support module.

Step 110 may be regarded as a calibration phase. During the calibrationphase the mechanical stage may be heated and cooled and the locationerrors as function of temperature of the mechanical stage is learnt. Thecalibration phase can include one or more calibration iterations,whereas the outcome of multiple calibration phases may be averaged ofprocessed in any other manner.

The calibration phase may be executed once or multiple times during thelifespan of the mechanical stage. For example—the calibration phase maybe repeated in a periodical manner, in response to events (such as anincrease in the number and/or magnitude of location errors), in a randomor in a pseudo-random manner.

Step 120 may include receiving the mapping between (i) values oftemperature information, (ii) estimated locations of a movable supportmodule, and (iii) location errors of the movable support module.

Steps 110 and 120 may be followed by step 130 of receiving, by acontroller, an estimated location of the movable support module andtemperature information.

Step 130 may include receiving the temperature information from atemperature sensor that senses a temperature of a certain portion of theobject support module.

Step 130 may include receiving the temperature information from multipletemperature sensors that sense temperatures of certain portions of theobject support module.

Step 130 may include receiving temperature timing information about atiming of acquisition of the temperature information.

Step 130 may include receiving the temperature information from atemperature sensor that is embedded in a Z axis stage.

Step 130 may be followed by step 140 of calculating, by the controller,movable support module location information, in response to (a) theestimated location of the movable support module, (b) the temperatureinformation and, (c) the mapping between (i) values of the temperatureinformation, (ii) locations of the movable support module, and (iii)location errors of the movable support module.

Step 140 may include, for example, applying at least one of thefollowing functions:

Correct(X,Y)=MAP {Estimated (X,Y), Temperature}.

Correct(X,Y)=MAP {Estimated (X,Y), Temperature, Timestamps}.

Correct(X,Y)=MAP {Estimated (X,Y), Temperature, Delta-Temperature}.

Step 140 may also include calculating a location of an optical axis ofan inspection or review tool in response to movable support modulelocation information.

Step 140 may also include calculating the movable support modulelocation information in response to temperature timing information.

Step 140 may also include calculating a change of the temperatureinformation over time.

Step 140 may also include calculating the movable support modulelocation information in response to the change of the temperature timinginformation over time.

Steps 130 and 140 may be regarded as a run time-phase in which thelocation errors are corrected according to the mapping that waspreviously received and/or calculated. The mapping may also be updatedaccording to outcomes of the runtime phase—taking into account locationerrors that were detected during the runtime phase. Averaging orfiltering of errors and outliers removal are beneficial in order not tointroduce errors in the mapping.

According to an embodiment of the invention, step 110 may includecalculating temperature patterns that are expected to be obtained duringcertain scan patterns. For example—the movable support module maygradually heat (by certain degrees) during a raster scan of the entireobject.

Yet for another example, changes in the speed of the movable supportmodule (for example changing from a X axis movement to a Y axismovement) may cause the movable support module to heat.

Yet for another example, slowing the movement of the movable supportmodule or even maintaining a constant speed across a scan line mayreduce the temperature of the movable support module.

Any temperature pattern may be taken into account (during step 140) whena certain scan pattern is detected.

FIG. 9 illustrates location errors before applying a temperaturesensitive location error correction. FIG. 9 includes a map 200 in whicheach location error of a wafer is represented by an out of scale arrowhaving a size and a direction that are indicative of a size anddirection of the location error.

FIG. 9 also illustrates a first graph 210 that represents statistics oflocation errors along an Y-axis of the wafer. The x-axis of the firstgraph 210 is indicative of sizes of location errors (in microns) and they-axis of the first graph 210 is indicative of the position (indecimeters) of the location errors along the Y-axis of the wafer. Thedecimeters are represented by microns multiplied by 105.

FIG. 9 also illustrates a second graph 220 that represents statistics oflocation errors along an X-axis of the wafer. The y-axis of the secondgraph 220 is indicative of sizes of location errors (in microns) and thex-axis of the second graph 220 is indicative of the position (indecimeters) of the location errors along the X-axis of the wafer. Thedecimeters are represented by microns multiplied by 105.

FIG. 10 illustrates location errors after applying a temperaturesensitive location error correction according to an embodiment of theinvention. FIG. 10 includes a map 300 in which each location error isrepresented by an out of scale arrow having a size and a direction thatare indicative of a size and direction of the location error. The arrowsof map 300 are substantially smaller than those of map 200.

FIG. 10 also illustrates a first graph 310 that represents statistics oflocation errors along an Y-axis of the wafer. The x-axis of the firstgraph 310 is indicative of sizes of location errors (in microns) and they-axis of the first graph 310 is indicative of the position (indecimeters) of the location errors along the Y-axis of the wafer. Thedecimeters are represented by microns multiplied by 105.

A comparison between first graph 210 of FIG. 9 and first graph 310 ofFIG. 10 illustrates that the sizes of the location errors along theY-axis of wafer of FIG. 10 are much smaller than the sizes of thelocation errors along the Y-axis of wafer of FIG. 9.

A comparison between second graph 220 of FIG. 9 and second graph 320 ofFIG. 10 illustrates that the sizes of the location errors along theX-axis of the wafer of FIG. 10 are much smaller than the sizes of thelocation errors along the X-axis of the wafer of FIG. 9.

FIG. 10 also illustrates a second graph 320 that represents statisticsof location errors along an X-axis of the wafer. The y-axis of thesecond graph 320 is indicative of sizes of location errors (in microns)and the x-axis of the second graph 320 is indicative of the position (indecimeters) of the location errors along the X-axis of the wafer. Thedecimeters are represented by microns multiplied by 105.

The invention may also be implemented in a computer program for runningon a computer system, at least including code portions for performingsteps of a method according to the invention when run on a programmableapparatus, such as a computer system or enabling a programmableapparatus to perform functions of a device or system according to theinvention. The computer program may cause the storage system to allocatedisk drives to disk drive groups.

A computer program is a list of instructions such as a particularapplication program and/or an operating system. The computer program mayfor instance include one or more of: a subroutine, a function, aprocedure, an object method, an object implementation, an executableapplication, an applet, a servlet, a source code, an object code, ashared library/dynamic load library and/or other sequence ofinstructions designed for execution on a computer system.

The computer program may be stored internally on a non-transitorycomputer readable medium. All or some of the computer program may beprovided on computer readable media permanently, removable or remotelycoupled to an information processing system. The computer readable mediamay include, for example and without limitation, any number of thefollowing: magnetic storage media including disk and tape storage media;optical storage media such as compact disk media (e.g., CD ROM, CD R,etc.) and digital video disk storage media; nonvolatile memory storagemedia including semiconductor-based memory units such as flash memory,EEPROM, EPROM, ROM; ferromagnetic digital memories; MRAM; volatilestorage media including registers, buffers or caches, main memory, RAM,etc.

A computer process typically includes an executing (running) program orportion of a program, current program values and state information, andthe resources used by the operating system to manage the execution ofthe process. An operating system (OS) is the software that manages thesharing of the resources of a computer and provides programmers with aninterface used to access those resources. An operating system processessystem data and user input, and responds by allocating and managingtasks and internal system resources as a service to users and programsof the system.

The computer system may for instance include at least one processingunit, associated memory and a number of input/output (I/O) devices. Whenexecuting the computer program, the computer system processesinformation according to the computer program and produces resultantoutput information via I/O devices.

In the foregoing specification, the invention has been described withreference to specific examples of embodiments of the invention. It will,however, be evident that various modifications and changes may be madetherein without departing from the broader spirit and scope of theinvention as set forth in the appended claims.

Moreover, the terms “front,” “back,” “top,” “bottom,” “over,” “under”and the like in the description and in the claims, if any, are used fordescriptive purposes and not necessarily for describing permanentrelative positions. It is understood that the terms so used areinterchangeable under appropriate circumstances such that theembodiments of the invention described herein are, for example, capableof operation in other orientations than those illustrated or otherwisedescribed herein.

The connections as discussed herein may be any type of connectionsuitable to transfer signals from or to the respective nodes, units ordevices, for example via intermediate devices. Accordingly, unlessimplied or stated otherwise, the connections may for example be directconnections or indirect connections. The connections may be illustratedor described in reference to being a single connection, a plurality ofconnections, unidirectional connections, or bidirectional connections.However, different embodiments may vary the implementation of theconnections. For example, separate unidirectional connections may beused rather than bidirectional connections and vice versa. Also,plurality of connections may be replaced with a single connection thattransfers multiple signals serially or in a time multiplexed manner.Likewise, single connections carrying multiple signals may be separatedout into various different connections carrying subsets of thesesignals. Therefore, many options exist for transferring signals.

Although specific conductivity types or polarity of potentials have beendescribed in the examples, it will be appreciated that conductivitytypes and polarities of potentials may be reversed.

Each signal described herein may be designed as positive or negativelogic. In the case of a negative logic signal, the signal is active lowwhere the logically true state corresponds to a logic level zero. In thecase of a positive logic signal, the signal is active high where thelogically true state corresponds to a logic level one. Note that any ofthe signals described herein may be designed as either negative orpositive logic signals. Therefore, in alternate embodiments, thosesignals described as positive logic signals may be implemented asnegative logic signals, and those signals described as negative logicsignals may be implemented as positive logic signals.

Furthermore, the terms “assert” or “set” and “negate” (or “deassert” or“clear”) are used herein when referring to the rendering of a signal,status bit, or similar apparatus into its logically true or logicallyfalse state, respectively. If the logically true state is a logic levelone, the logically false state is a logic level zero. And if thelogically true state is a logic level zero, the logically false state isa logic level one.

Those skilled in the art will recognize that the boundaries betweenlogic blocks are merely illustrative and that alternative embodimentsmay merge logic blocks or circuit elements or impose an alternatedecomposition of functionality upon various logic blocks or circuitelements. Thus, it is to be understood that the architectures depictedherein are merely exemplary, and that in fact many other architecturesmay be implemented which achieve the same functionality.

Any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality may be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated can also be viewed as being “operably connected,” or“operably coupled,” to each other to achieve the desired functionality.

Furthermore, those skilled in the art will recognize that boundariesbetween the above described operations merely illustrative. The multipleoperations may be combined into a single operation, a single operationmay be distributed in additional operations and operations may beexecuted at least partially overlapping in time. Moreover, alternativeembodiments may include multiple instances of a particular operation,and the order of operations may be altered in various other embodiments.

Also for example, in one embodiment, the illustrated examples may beimplemented as circuitry located on a single integrated circuit orwithin a same device. Alternatively, the examples may be implemented asany number of separate integrated circuits or separate devicesinterconnected with each other in a suitable manner.

Also for example, the examples, or portions thereof, may implemented assoft or code representations of physical circuitry or of logicalrepresentations convertible into physical circuitry, such as in ahardware description language of any appropriate type.

Also, the invention is not limited to physical devices or unitsimplemented in non-programmable hardware but can also be applied inprogrammable devices or units able to perform the desired devicefunctions by operating in accordance with suitable program code, such asmainframes, minicomputers, servers, workstations, personal computers,notepads, personal digital assistants, electronic games, automotive andother embedded systems, cell phones and various other wireless devices,commonly denoted in this application as ‘computer systems’.

However, other modifications, variations and alternatives are alsopossible. The specifications and drawings are, accordingly, to beregarded in an illustrative rather than in a restrictive sense.

In the claims, any reference signs placed between parentheses shall notbe construed as limiting the claim. The word ‘comprising’ does notexclude the presence of other elements or steps then those listed in aclaim. Furthermore, the terms “a” or “an,” as used herein, are definedas one or more than one. Also, the use of introductory phrases such as“at least one” and “one or more” in the claims should not be construedto imply that the introduction of another claim element by theindefinite articles “a” or “an” limits any particular claim containingsuch introduced claim element to inventions containing only one suchelement, even when the same claim includes the introductory phrases “oneor more” or “at least one” and indefinite articles such as “a” or “an.”The same holds true for the use of definite articles. Unless statedotherwise, terms such as “first” and “second” are used to arbitrarilydistinguish between the elements such terms describe. Thus, these termsare not necessarily intended to indicate temporal or otherprioritization of such elements. The mere fact that certain measures arerecited in mutually different claims does not indicate that acombination of these measures cannot be used to advantage.

While certain features of the invention have been illustrated anddescribed herein, many modifications, substitutions, changes, andequivalents will now occur to those of ordinary skill in the art. It is,therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the invention.

What is claimed is:
 1. A system comprising: a movable support module forsupporting an object; and a controller configured to: receive anestimated location of a movable support module that supports an object,and temperature information about an actual or estimated temperature ofat least a portion of the object support module; and calculate movablesupport module location information, in response to (a) the estimatedlocation of the movable support module, (b) the temperature informationand, (c) a mapping between (i) values of the temperature information,(ii) estimated locations of the movable support module, and (iii)location errors of the movable support module.
 2. The system accordingto claim 1 wherein the controller is configured to calculate themapping.
 3. A method for temperature sensitive location errorcompensation, the method comprising: receiving, by a controller, anestimated location of a movable support module that supports an object,and temperature information about an actual or estimated temperature ofat least a portion of the object support module; and calculating, by thecontroller, movable support module location information, in response to(a) the estimated location of the movable support module, (b) thetemperature information, and (c) a mapping between (i) values of thetemperature information, (ii) locations of the movable support module,and (iii) location errors of the movable support module.
 4. The methodaccording to claim 3 comprising calculating a location of an opticalaxis of an inspection or review tool in response to the movable supportmodule location information.
 5. The method according to claim 3comprising generating the mapping by measuring the location errors ofthe movable support module at different actual or estimated temperaturesof the movable support module.
 6. The method according to claim 5comprising heating the movable support module by a heating element toobtain at least some of the different actual or estimated temperaturesof the movable support module.
 7. The method according to claim 5comprising heating the movable support module by moving the movablesupport module during a period of time that exceeds a predeterminedthreshold to obtain at least some of the different actual or estimatedtemperatures of the movable support module.
 8. The method according toclaim 5 comprising cooling the movable support module by a coolingelement to obtain at least some of the different actual or estimatedtemperatures of the movable support module.
 9. The method according toclaim 5 wherein the estimated location of the movable support module isprovided by a location monitor; wherein the temperature information isprovided by a temperature sensor that is located at a certain position;wherein the generating of the mapping comprises estimating arelationship between a temperature sensed by the temperature sensor anda temperature of a part of the location monitor.
 10. The methodaccording to claim 3 comprising receiving the temperature informationfrom a temperature sensor that senses a temperature of a certain portionof the object support module.
 11. The method according to claim 3comprising receiving the temperature information from multipletemperature sensors that sense temperatures of certain portions of theobject support module.
 12. The method according to claim 3 furthercomprising receiving temperature timing information about a timing ofacquisition of the temperature information; and wherein the calculatingof the movable support module location information is also responsive tothe temperature timing information.
 13. The method according to claim 12further comprising calculating a change of the temperature informationover time; and wherein the calculating of the movable support modulelocation information is also responsive to the change of the temperaturetiming information over time.
 14. The method according to claim 3further comprising: receiving or calculating a relationship between ascan pattern that is followed by the movable support module and betweentemperatures obtained during the scan pattern; detecting that themovable support module started to follow the scan pattern; andcalculating the movable support module location information in responseto the relationship.
 15. The method according to claim 3 wherein themovable support module comprises an X-Y axis stage and a Z axis stage;wherein the movable support module location information is indicative ofa location of the movable support module within an X-Y plane; andwherein the temperature information is provided by a temperature sensorsembedded in the Z axis stage.
 16. A non-transitory computer readablemedium that stores instructions that once executed by a computer causethe computer to: receive an estimated location of a movable supportmodule that supports an object, and temperature information about anactual or estimated temperature of at least a portion of the objectsupport module; and calculate movable support module locationinformation, in response to (a) the estimate location of the movablesupport module, (b) the temperature information and, (c) a mappingbetween (i) values of the temperature information, (ii) estimatelocations of the movable support module, and (iii) location errors ofthe movable support module.